To realize the promise of gene therapy as a treatment modality for cancer, we must develop simplified but effective gene delivery approaches and understand how therapeutic proteins act to kill tumors. Our proposal directly addresses both of these critical elements. We have pioneered the use of muscle-based electroporation as a novel and inexpensive approach for simplified and effective gene delivery and have demonstrated that injection of the IL-12 gene to muscle accompanied by electroporation substantially enhances the level of IL-12 expression and its systemic antitumor efficacy, compared with injection without electroporation, leading to 20% eradication of tumors located distant to the gene injection site. We hypothesize that delivery of IL-12 DNA via intramuscular electroporation, in synergy with a novel muscle-specific expression system, will eradicate or inhibit remote squamous cell carcinoma (SCC) by upregulation of antitumor genes. Our long-term goal is to develop a simple and effective strategy for eradicating inaccessible small-load metastatic SCC or residual microscopic SCC after surgery. We will use a tumor model of SCC, known as SCCVII, which allows the generation of both subcutaneous and metastatic tumors in a syngeneic murine host (C3H/HeJ) to explore the following Specific Aims. Aim 1: Determine the optimal delivery and expression system for electroporation to achieve therapeutic levels of IL-12 in vivo, and assess the systemic toxicity of gene therapy in comparison to protein therapy. Aim 2: Determine the role of Stat 1 and primary immune cells in inhibition of tumor growth elicited by IL-12. This work holds enormous potential for progress in eradicating SCC, particularly in those clinical situations where small-load metastases are inaccessible or in cases where residual microscopic disease persists after surgery. The experiments that we propose have a high probability of success because we have an excellent model system in place, experience in the electroporation gene therapy field, and all the resources necessary to complete the task.